From the Grand Balcon Nord: Plan de l’Aiguille to Montenvers
, take the steep switchbacks up several hundred feet before level off and curving around to huge views of the Montets and then the Mer de Glace. There is a huge field of cairns that seems to amuse people... Follow them right to the western edge for the best views of the pointy spires in all directions.
After soaking it in, continue on to the north and follow the switchbacks down to the train station.